Means for operating antennas



1956 J. M. TEWKSBURY ET AL 2,761,134

MEANS FOR OPERATING ANTENNAS Filed Jan. 18, 1952 I 3 Sheets-Sheet 1 FIG.E

ll l3- '2 as 33 I9 I PULSE 4 RECVR 32 GEN 34 Q 3 humus cur v *ol=r 3o I?29 2a EF 2 DEFLEC- l I TION AMPLR SAW I GEN M I I o DEFLEC- 1 I now QAMPLR i L INVENTORS JOHN M.TEWKSBURY PPI S EE GEN ALFRED AHEMPHILLATTORNEYS Aug. 28, 1956 J. M. TEWKSBURY ET AL 2,761,134

MEANS FOR OPERATING ANTENNAS Filed Jan. 18, 1952 3 Sheets-Sheet 2 FIG. 3

MAGNETIZATION CURVE CYCLE I INVENTORS JOHN M.TEWKSBURY ALFRED A.HEMPHILL haw/24%;

ATTORNEYS Aug. 28, 1956 J. M. TEWKSBURY ET 2,761,134

MEANS FOR OPERATING ANTENNAS Filed Jan. 18, 1952 3 Sheets-Sheet 3 FIG. 6

INVENTORS JOHN M. TEWKSBURY ALFRED A.HEMPH|LL f wwawmaluzif ATTORNEYSUnite States Patent L'IEANS FOR OPERATING ANTENNAS John M. Tewksbury andAlfred A. Hemphill, Baltimore,

Md., assignors to Bendix Aviation Corporation, Towson, Md., acorporation of Delaware Application January 18, 1952, Serial No. 267,093

4 Claims. (Cl. 343121) This invention relates generally to electricantennas and more particularly to a new method and means for operatingsuch antenna elements in the neighborhood of resonance so as to producein a simple and efficient manner results which have been heretoforeunattainable.

It is well known that electric antennas have operational characteristicswhich are critically dependent upon the physical dimensions of theradiating elements and the circuit and space parameters associatedtherewith. Many prior art antenna systems have been devised which relyfor their operation upon specific proportions and arrangements ofradiating elements and upon the adjustment or variation of these andother circuit parameters for attaining the desired performance.

A Well known arrangement of this general type is the Yagi antenna array.In the Yagi array, a highly directive unidirectional radiating patternis obtained by the use of parasitic radiating elements commonly referredto as directors and reflectors. By interchanging the directors andreflectors, a mirror image of the radiating pattern will be obtained.

Other antenna systems provide means for energizing all of the elementsin the system. With the proper physical arrangement of elements and theproper phase relationship of the signals radiated therefrom, it ispossible to provide a rotating radiating pattern.

The above described arrangements present certain limitations or inherentcharacteristics that are at times undesirable. The Yagi antenna systemis limited to one of two possible positions of the radiating pattern,while if the latter systems are to provide rotating patterns, energymust be provided to all of the elements. Providing energy to all of theelements necessitates providing signal carrying leads thereto. Theseadditional leads, because of the physical displacements of the elementswith respect to each other, cannot at all times be arranged such thatthe field does not affect the signals contained therein.

The present invention provides an antenna system that does not havethese limitations. In this system, a rotating radiating pattern isprovided that has the highly directive characteristics and parasiticelements of a Yagi antenna array and the controllable rotationalcharacteristics of an antenna system that has individually energizedradiating elements. In effect, a rotating pattern is produced byelectronic means that is equivalent to the rotating pattern that isobtained by physically rotating a Yagi antenna array.

The particular embodiment of the invention as depicted in the drawingsprovides, in the antenna elements, variable impedances which directlyaffect the performance thereof in the neighborhood of resonance. By theparticular physical arrangement and control of the variable impedancesto be explained in discussing the drawings, the parasitic elements havetheir electrical lengths sequentially varied to produce, in effect, arotating Yagi antenna array.

It is accordingly an object of this invention to provide 2 an antennasystem for producing a rotating radiating pattern.

A further object is to provide an antenna system for producing arotating radiating pattern that is highly sensitive and directive innature.

A still further object is to provide an antenna system for producing arotating radiating pattern that does not necessitate providing energy tonor receiving energy from more than one element in the system.

These and other objects of the invention will be more clearly understoodby reference to the following detailed description taken in conjunctionwith the following .drawings wherein:

Fig. 1 is a plan view of an electric dipole having a controlledreactance element;

Fig. 2 is a view representing a system in accordance with the invention;

Fig. 3 is a diagram showing magnetic properties;

Fig. 4 is a plan view of the antenna system of Fig. 2 showing thepattern;

Fig. 5 is a diagram of received signal voltages; and

Fig. 6 is a perspective view of the direction finder of Fig. 2.

Referring to Fig. 1, there is shown a center fed dipole 11 having acentrally connected inductance coil 12. The inductance coil 12 has atleast a portion thereof wound on a core 13, the permeability of which isa factor in determining the total value of inductance in the antenna.The antenna assembly 1112 is provided with suitable signal frequencyenergy coupling means, as for example a coil 14, coupled to a portion ofthe coil 12 which is not wound on the core 13, the coupling, therefore,being independent of the value of the permeability. Also wound on thecore 13 is a permeability control coil 15 which is energized by a lowfrequency current from a suitable source 16. The value of the currentmay be controlled by means of a rheostat control 17.

The core 13 is composed of a suitable high frequency permeable materialwhich provides a relatively high value of permeability, the value ofwhich varies with the degree of saturation flux present in the core.Such characteristics are provided, for example, by dust iron corematerial or preferably from the class of materials known as ferrites,for example, as Stackpole Ceramag 4.

In the operation of the antenna of Fig. l, signals are coupled to orfrom the antenna coupling coil 14, respectively, as the device is usedfor transmission or reception. By the adjustment of the control 17 thevalue of inductance of the coil 12 may be selected within predeterminedlimits in response to the degree of saturation of the core 13 due to thesaturating current in the coil 15. The antenna assembly 11-12 is thusbrought into any desired degree of resonance by means of an electricalcontrol condition. Obviously, the tuning control 17 could be ganged withtuning controls in other portions of the transmitter or receivercircuits in a manner to secure the desired correspondence between all ofthe tuned elements and circuits. In like manner the tuned antenna of theinvention can be employed in automatic or in signalseeking tunerapplications since tuning may be accomplished under the control of anelectrical condition and without mechanical adjustment in the vicinityof the antenna structure.

Referring to Fig. 2, there is shown a ground-based direction findersystem in accordance with the present invention. The vsystem comprises acenter antenna system 19 similar to that of Fig. 1 and four radiallydisposed parasitic antenna elements 21, 22, 23, 24 having approximatelyA/S spacing from the center antenna 19. The parasitic elements .2l-.-24are similar to the system 19, except that no signal coupling means areemployed to derive energy by direct circuit therefrom. The saturationcoils of the even and odd numbered parasitic element pairs are connectedto different phases of a generator having sinusoidal output voltageswhich are in 90 phase relation. The connections to the coils of a pairare oppositely phased so that diametrically arranged elements areenergized with 180 phae relation. Tuning adjustments 26-, 27 areprovided for initially setting the saturation current for each pair ofthe elements 21-24, together with such trimming adjustments 28, 29 asare required to initially adjust the individual elements 21-24 tosuitable operating points on the magnetization curves of the coresthereof. Adjustable resistors 28, 29 may be duplicated in oppositesaturation circuits of each pair, if required.

The output voltages of the generator 25 are applied to a P. P. I. sweepgenerator 31, the outputof which is applied to control the sweep of acathode ray indicator 32., This sweep provides a radial linepresentation on the indicator which rotates at a frequency equal to thatof the generator 25. The indicator 32 is normally biased to cutofi sothat no indication appears except as hereinafter described.

The signal frequency energy received by the central antenna 19 iscoupled to a receiver 33. The receiver 33 is provided with a tuningcontrol 34 which may be ganged with a saturation tuning adjustment ofthe antenna 19, and if desired, by suitable linkage to the controls 26,27. With this arrangement, tuning the receiver will adjust antenna 19 toresonance at the receiver frequency and also the elements 21-24 for thecondition of zero saturation current from the generator 25. Signals fromthe receiver 33 are supplied to a pulse generator 35. The pulsegenerator 35 provides a pulse output which bears a predetermined phaserelation to the amplitude variations of the output of receiver 33 whichare due to the rotation of the antenna pattern, as will be more fullyexplained hereinafter.

The operation of the system. of Fig. 2 will be described with referenceto Figs. 3 and 4. represents the incremental permeability of the corematerial employed, for various values of the magnetizing force H. Anoperating point P0 is established on the curve for each core in theantenna 19 and parasitic ele- In Fig. 3 the function p.

ments 21-24 by means of, the D. C. controls 26-29.

I, as a director or reflector and, since its diametrical oppositeelement is saturated with 180 phase relation, an aiding reflector anddirector condition obtains. For this condition a maximum receptiondirection exists along the diameter of the oppositely phased elements asshown in Fig. 4 by antenna pattern 36. As the current from generator 25varies sinusoidally in the saturation coils of the parasitic elements,the directive pattern 36 rotates as indicated by the arrow. Thisrotation occurs due to the phase of the saturation currents in theparasitic elements 2124. From the condition depicted at 36 in Fig. 4the. currents change in a manner to reduce the directivity of element22and increase that of element 23. correspondingly the reflectivity ofelement 24 is reduced and that of element 21 increased. These actionscombine to direct the radiation pattern in a position intermediate theelements 22, 23 as shown by pattern 36'. After a 90 time interval fromthe instant the pattern is directed as shown at 36 the radiation will bedirected along the diameter through elements 21, 23 and in the directionof element 23. Thus, it can be seen that a progressive rotation of theantenna directivity occurs throughout 360 in space for-each cycle of thegenerator 25. Inasmuch as no mechanical motion is involved in theantenna structure, the speed of pattern rotation may be made quite high,thus giving substantially continuous information from relatively fixedsources, such as aircraft.

The rotation of the antenna pattern as shown in Fig. 4 results, as shownin Fig. 5, man output signal 37 in the receiver 33 for a single fixedradio signal source. This signal 37 occurs as the antenna pattern 36sweeps over a line joining the antenna 19 and the aircraft source. Bysuitably establishing a direction convention for the radial sweep of theindicator 32 an intensified radial sweep may be obtained to indicate thedirection of the source. This result may be accomplished by pulsesproduced from the pulse generator 35 for each peak value of the signals37 of predetermined amplitude to produce the desired indication on theindicator 32.

Referring now to Fig. 6, there is shown a mast 33 supporting a groundplane quarter-waverantenna 19 and the parasitic elements 21-44. Theparasitic elements are mounted in housings 39 which contain thesaturation cores 13 as shown in the cutaway view of element 22. Radiofrequency energy is coupled to the antenna 19' by means of a suitabletransmission line 41 and saturation currents to all control coils aresupplied by means of multiconductor cable 42. It will be apparent thatthis arrangement provides an antenna system which is immune fromdifficulties due to a horizontal polarization component of the receivedwave, since no horizontal projections are coupled to the line 41 atradio frequencies.

Obviously, many modifications can be made in the light of the aboveteachings without departing from. the spirit and scope of the present,invention. These principles may be incorporated in other Well knownparasitic or driven array configurations and are not limited to thepresent particular embodiment, here shown by way of example. Certainapplications may require the use of a carrier wave of, say, 10,000 C. P.S. for the saturation signal in a manner which is well known as, forexample, in the magnetic tape recording art.

What is claimed is:

1. A radiant energy transducer system for producing a rotating directivepattern, comprising: a central vertical antenna; an even number ofidentical parasitic antenna radiators; said number being at least four;means associated with each of the said radiators providing control ofthe electrical length thereof; said radiators being symmetricallydisposed in a circle about the said antenna; a second means; said secondmeans operating upon each of said control means in a manner such thatthe said electrical lengths of the said radiators that are diametricallydisposed with respect to one another are varied in phase opposition; thephase displacements between the variations of the said radiators beingequal to the angular physical displacement therebetween; a radiofrequency signal means; and means for cotiplingradio frequency energyfrom the said antenna to the last said means.

2. A radiant energy transducer system for producing a rotating directivepattern, comprising: a central vertical antenna; an even number ofidentical parasitic antenna radiators; said number being at least four;means associated with each of the said radiators providing control ofthe electrical length thereof; said means comprising variable lumpedreactors; said radiators being symmetrically disposed in a circle aboutthe said .antenna; a second means; said second means operating upon eachof said control means in a manner such that the saidelectrical lengthsof the said radiators that are diametrically disposed with respect toone another are varied in phase opposition; the phase displacementsbetween the variations of the said radiators being equal to the angularphysical displacement therebetween; a radio frequency signal means; andmeans for coupling radio frequency energy from the said antenna to thelast said means.

3. A radiant energy transducer system for producing a rotating directivepattern, comprising: a central vertical antenna; an even number ofidentical parasitic antenna radiators; said number being at least four;means associated with each of the said radiators providing control ofthe electrical length thereof; said means comprising inductance coilshaving variable permeable cores with saturating windings thereon; saidradiators being symmetrically disposed in a circle about the saidantenna; a second means; said second means operating upon each of saidcontrol means in a manner such that the said electrical lengths of thesaid radiators that are diametrically disposed with respect to oneanother are varied in phase opposition; the phase displacements betweenthe variations of the said radiators being equal to the angular physicaldisplacement therebetween; a radio frequency signal means; and means forcoupling radio frequency energy from the said antenna to the last saidmeans.

4. A radiant energy transducer system for producing a rotating directivepattern, comprising: a central vertical antenna; an even number ofidentical parasitic antenna radiators; said number being at least four;means associated with each of the said radiators providing control ofthe electrical length thereof; said means comprising inductance coilshaving variable permeable cores with saturating windings thereon; asignal generating means; means coupling the said generating means to thesaid References Cited in the file of this patent UNITED STATES PATENTS2,072,267 Kramar Mar. 2, 1937 2,199,819 Galle May 7, 1940 2,212,245Perroux Aug. 20, 1940 2,238,261 Hahnernann Apr. 15, 1941 2,254,943 GalleSept. 2, 1941 2,419,987 Carlson May 6, 1947 2,581,348 Bailey Jan. 8,1952 OTHER REFERENCES Radio Craft for July 1939, pages 13 and 51. Tuningwith a Rheostat, by G. Leithauser and H. Boucke.

